1. Field of the Invention
The present invention relates to multilayer capacitors using capacitor bodies in which internal electrodes are layered with dielectric layers sandwiched therebetween. More particularly, the present invention relates to a multilayer capacitor having an improved arrangement of dielectric layers sandwiched between internal electrodes connected to different voltages.
2. Description of the Related Art
Various multilayer capacitors are in widespread use in electric apparatuses. Japanese Unexamined Patent Application Publication No. 8-69939 discloses a multilayer capacitor shown in FIG. 11. A multilayer capacitor 101 includes a capacitor body 102 manufactured by layering multiple ceramic green sheets and firing the layered ceramic green sheets. Multiple internal electrodes 103a to 103d are arranged in the capacitor body 102 so as to be overlapped with each other with ceramic dielectric layers sandwiched therebetween. The ceramic dielectric layers define the capacitor body. The internal electrodes 103a and 103c extend to one end 102a of the capacitor body 102 and the internal electrodes 103b and 103d extend to the other end 102b thereof. External electrodes 104 and 105 are provided so as to cover the one end 102a and the other end 102b, respectively.
The shapes of the internal electrodes, the thicknesses of the dielectric layers, the sizes of the capacitor body, and other characteristics are adjusted in the multilayer capacitor of this type so as to prevent occurrences of cracks as the temperature of the multilayer capacitor varies and to prevent occurrences of cracks caused by breakdown due to any mechanical stress applied to the multilayer capacitor. Various multilayer capacitors are disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-124057, Japanese Unexamined Patent Application Publication No. 6-163311, Japanese Unexamined Patent Application Publication No. 8-181033, Japanese Unexamined Patent Application Publication No. 11-150037, and Japanese Unexamined Utility Model Registration Application Publication No. 7-32936.
As described above, the thicknesses of the dielectric layers, the shapes and sizes of the internal electrodes, and other characteristics have been changed in the multilayer capacitor so as to prevent occurrences of cracks caused by any mechanical stress applied to the multilayer capacitor.
Reduction in size of the multilayer capacitors is increasingly required, as in other electric apparatuses. Accordingly, it is highly desirable to promote the reduction in size and increase in capacitance of the multilayer capacitors.
In order to increase the capacitance of the multilayer capacitors, the proportion of portions in which the internal electrodes connected to different voltages are overlapped with each other with the dielectric layers sandwiched therebetween should be increased.
During driving of the multilayer capacitors, vibrations attributed to electrostriction can be caused in the dielectric layers connected to different voltages. In particular, the vibration attributed to the electrostriction is likely to increases when the proportion of the portions, in which the internal electrodes connected to different voltages are overlapped with each other with the dielectric layers sandwiched therebetween, is increased in order to promote the increase in capacitance of the multilayer capacitors. As a result, the substrates on which the multilayer capacitors are mounted may vibrate to produce an undesired sound, that is, a sound caused by the substrate vibration and/or to damage the portions at which the multilayer capacitors are mounted on the substrates.